The emission band system c2 Σ + — x2 Π of NH+

Five red degraded bands belonging to theC ² Σ ⁺ —X ² Π system of NH⁺ were excited in a mild condensed discharge through flowing ammonia and were photographed on a 3.4 meter Ebert grating spectrograph at a dispersion of 2.5 A/mm. The rotational analyses of these bands enabled us to evaluate the vibrational and rotational constants accurately. The rotational energy levels of theΠ ⁺ andΠ ⁻ levels of theν=0 and 1 levels of the ground state,X ² Π, were fitted in James expression using two sets of rotational constants. The perturbations observed in theX ² Π state caused by thea ⁴ Σ ⁻ state were examined in greater detail.     

NaNe potentials from a combined analysis of spectroscopic and scattering data

Experimental differential cross sections for the optical collision process Na(3s)+Ne+hν→Na(3p)+Ne and spectroscopic data for A²Π→X²Σ⁺optical transitions are used to obtain the potential curves for the X²Σ⁺ground and A²Π first excited states of the NaNe molecule and the spin-orbit function g_so(r).     

The collisional energy transfer between the D1Π and d3Π states of the NaK dimer induced by argon buffer gas

1 Π→X¹Σ⁺ transitions and the continuum spectrum of d³Π→a³Σ⁺ transitions of the NaK dimer in a heat pipe could be observed in the range of 500–700 nm. The collision-induced enhancement effects of the intensities I_d→a and the quenching effect of the intensities I_D→X by collisions with argon buffer gas at different pressures were measured experimentally. Based on the stationary collisional model and lifetime measurements, the quenching cross sections and cross sections for collision-induced energy transfer between the D¹Π and d³Π states could be estimated. Received: 13 January 1997/Revised version: 20 October 1997     

Hyperfine interactions in molecules through laser spectroscopy

The infrared and millimeter wave spectroscopy, laser Stark spectroscopy, and beam maser spectroscopy of CH₃CN and its isotopic species will be discussed. The beam maser spectroscopy and hyperfine structure of molecules like NCCCD, ClCCD and CH₃CCH are reviewed. The laser magnetic resonance and hyperfine structure in CF, CH and CH₂ free radicals will be discussed. The Lamb dip spectroscopy and laser-induced fluorescence in I₂ involving theB ³Π(0 _u ⁺ ) state are reviewed with special reference to its hyperfine structure. The splitting of the rotational levels of N ₂ ⁺ in itsX ²Σ _g ⁺ andB ²Σ _u ⁺ states due to hyperfine interactions (along with the hyperfine structure) in laser-induced fluorescence in theB−X transition is discussed. Recent results obtained in the laser photo-acoustic spectrum of ICl in the transitionX ¹Σ⁺ −A ³Π₁ will be presented and the possibility of the use of this technique in studying the hyperfine structure will be discussed.     

Studies on the full vibrational energy spectra for some electronic states of diatomic molecular ions XY+

The first accurate studies on the vibrational spectroscopic constants and the corresponding full vibrational energy spectra of some electronic states of diatomic molecular ions XY⁺ were performed using algebraic method(AM). The AM is applied on the X¹Σ⁺ state of BeH⁺, the X²Σ⁺ state of CO⁺, the X²Π_g state of F ₂ ⁺ , the A²Π_u state of O ₂ ⁺ and the X²Σ _g ⁺ state of Li ₂ ⁺ . The results show that AM can generate accurate vibrational spectroscopic constants as well as accurate full vibrational energy spectra by using some accurate experimental vibrational energies, and that the AM vibrational energies are better than other theoretical data. __________ Translated from Chinese Journal of Atomic and Molecular Physics, 2005, 22 (4) (in Chinese)     

Calculation of spectroscopic constants and radiative parameters for A1Σ u+ -X1Σ g+ and B1Πu-X1Σ g+ electronic transitions of sodium dimer

Vibrational, rotational, and centrifugal spectroscopic constants and radiative parameters, i.e., the Einstein coefficients, oscillator strengths, and wave numbers for vibrational transitions in electronic systems of bands A ¹Σ _u ⁺-X ¹Σ _g ⁺ (0 ≤ v′ ≤ 25; 0 ≤ v″ ≤ 44), B ¹Π _u -X ¹Σ _g ⁺ (0 ≤ v′ ≤ 29; 0 ≤ v″ ≤ 47), and the radiative lifetimes for the vibrational levels of excited states of the sodium dimer, are calculated. The calculations are carried out based on semiempirical potential curves constructed in this study. The calculated spectroscopic constants and radiative lifetimes are compared to the experimental values.     

Calculation of the spectroscopic constants for the electronic states A1Σ u+ , B1Πu, C1Πu, D1Σ u+ , and E1Σ u+ of the cesium dimer

The vibrational, rotational, and centrifugal distortion constants have been calculated for the electronic states A ¹Σ _u ⁺ , B ¹Π_u, C ¹Π_u, D ¹Σ _u ⁺ , and E ¹Σ _u ⁺ of the Cs₂ molecule. The calculation was performed on the basis of the semiempirical potential energy curves constructed in this paper. The calculated spectroscopic constants are compared with the experimental data. Original Russian Text ? A.D. Smirnov, 2007, published in Optika i Spektroskopiya, 2007, Vol. 102, No. 1, pp. 23–27.     

Spectroscopy of the a3Σu + state and the coupling to the X1Σg + state of K2

We report on high resolution Fourier-transform spectroscopy of fluorescence to the a³Σ_u ⁺ state induced by two-photon or two-step excitation from the X¹Σ_g ⁺ state to the 2³Π_g state in the molecule K₂. These spectroscopic data are combined with recent results of Feshbach resonances and two-color photoassociation spectra for deriving the potential curves of X¹Σ_g ⁺ and a³Σ_u ⁺ up to the asymptote. The precise relative position of the triplet levels with respect to the singlet levels was achieved by including the excitation energies from the X¹Σ_g ⁺ state to the 2³Π_g state and the frequencies of the fluorescence down to the a³Σ_u ⁺ state in the simultaneous fit of both potentials. The derived precise potential curves allow for reliable modeling of cold collisions of pairs of potassium atoms in their ²S ground state. Electronic supplementary material Supplementary Online Material     

Fluorescence studies of CS2 and SO2 at 121.6, 73.6–74.4 and 58.4 nm

The fluorescence spectra of CS₂ and SO₂ have been studied at three incident photon wavelengths of 121.6, 73.6–74.4 and 58.4 nm and relative production cross sections for different product states have been measured. The CS(A ¹Π→X ¹Σ⁺) system between 240 and 290nm has been obtained when CS₂ is photoexcited at 121.6nm whereas CS ₂ ⁺ (B ²Σ _u ⁺ →X ²Π _g ) and CS ₂ ⁺ (A ²Π _u →X ²Π _g ) systems have been produced between 276 and 295 and 437 and 555nm respectively when excited by both the incident photon wavelengths of 73.6–74.4 and 58.4nm. The fluorescence spectra of SO₂ obtained at 121.6 and 73.6–74.4nm include the vibrational bands of SO(A ³Π→X ³Σ⁻) and SO(B ²Π⁻→X ³Σ⁻) systems from 240 to 268 and 268 to 442nm respectively whereas the emission spectrum at 58.4nm, has contributions from the two SO systems and SO⁺(A ²Π→X ²Π) system. In all these emission spectra, the fluorescence bands of different systems have been analyzed and their relative production cross sections have been measured. The results obtained in the present investigations have been compared with a few recent reliable measurements reported in literature.     

Emission spectroscopy of the A<Superscript>1</Superscript>Π–X<Superscript>1</Superscript>Σ<Superscript>+</Superscript> system of AlH

The high-resolution emission spectrum of the A¹ Π–X¹Σ⁺ transition of AlH was observed in the 18 000–25 000 cm^-1 spectral region using a conventional spectroscopic technique. The AlH molecules were excited in an Al hollow-cathode lamp filled with a mixture of Ne carried gas and a trace amount of NH₃. The emission from the discharge was observed with a plane grating spectrograph and recorded by a photomultiplier tube. In total 163 transition wave numbers belonging to six bands (0-0,1 and 1-0,1,2,3) were precisely measured and rotationally analysed. In the final fit the present data have been combined with available high-resolution measurements of the vibration-rotation bands by White et al. [J. Chem. Phys. 99, 8371 (1993)]. This procedure enabled extracting molecular constants for the A¹ Π and X¹ Σ⁺ states of AlH. A very slight local perturbation has been discovered in the v=1 vibration level of the A¹ Π state at J=5. This was probably caused by the interaction with the a³Π state.     

Spectroscopic study of rotational energy distribution of BH (A 1Π) and electronic excitation temperature determination

Emission spectra of BH(A ¹Π-X ¹Σ⁺) system were recorded and studied using a low pressure (3.0 torr) arc in flowing hydrogen and argon + hydrogen mixture. The rotational distributions in theA ¹Π state determined from the intensities of rotational lines for the 0–0 band of theA-X system conforms to a Maxwellian distribution with effective rotational temperature of 1000 ± 50°K. Intensities of Balmer lines of hydrogen were measured and used to determine electronic excitation temperature which was found to be around 2000°K.     

Measurement of OH spatially resolved spectrum in a wire-plate pulsed streamer discharge

In this study, spatially resolved measurements of the emission intensity of OH (A²Σ↦X²Π, 0-0) and the vibrational temperature of N₂ (C) have been performed during a positive pulsed streamer discharge with a wire-plate electrode configuration at atmospheric pressure. The effects of pulse peak voltage, pulse repetition rate and the added O₂ flow rate on the spatial distributions of the emission intensity of OH (A²Σ↦X²Π, 0-0) and the vibrational temperatures of N₂ (C) perpendicular to the wire in the direction towards the plate (in the radial direction) are investigated. It has been found that the emission intensity of OH (A²Σ↦X²Π, 0-0) increases with increasing pulse peak voltage and pulse repetition rate and decreases with increasing the distance from the wire electrode. When the different oxygen flows are added in N₂ and H₂O mixture gas, the emission intensity of OH (A²Σ↦X²Π, 0-0) decreases with increasing the flow rate of oxygen. The vibrational temperature of N₂ (C) is nearly independent of pulsed peak voltage and pulsed repetition rate, but increases with increasing the added O₂ flow rate and keeps almost constant in the radial direction under the present experimental conditions. This measurement plays a crucial role in understanding the discharge characters of pulsed streamer discharge and establishing the molecule reaction dynamics model of pulsed streamer discharge.     

2-D absolute OH concentration profiles in atmospheric flames using planar LIF in a bi-directional laser beam configuration

1 (6) rotational line in the A²Σ⁺(v^′=0)←X²Π(v^′′=0) band of OH at 309 nm. The requirements for obtaining a good signal-to-noise ratio for the technique are discussed and the possibilities of single-shot measurements are investigated. Received: 31 October 1996/Revised version: 3 December 1996     

Λ(1405) as a multiquark state

In the QCD sum rule approach we predict the Λ (1405) mass by choosing the π⁰Σ⁰ multiquark interpolating field. It is found that the mass is about 1.419 GeV from Π₁ (q ²) sum rule which is more reliable than Π_q (q ²) sum rule, where Π_q (q ²) and Π₁ (q ²) are two invariant functions of the correlator Π (q ²). We also present the sum rules for the K ⁺ p and the π⁺Σ⁺ multiquark states, and compare to those for the π⁰Σ⁰ multiquark state. The mass of the Λ (1600) can be also reproduced in our approach. Received: 11 November 1997 / Revised version: 28 April 1998     

High-resolution F T spectrum of A2Πr-X2Σ+ band system of MgCl

The emission spectrum of the A ² Π _r -X ² Σ ⁺ band system of MgCl molecule (360–380 nm) has been recorded on BOMEM DA8 Fourier transform spectrometer at an apodized resolution of 0.035 cm⁻¹. The spectra have been excited under flowing conditions in a demountable stainless steel hollow cathode lamp (400 V, 250 mA) containing anhydrous MgCl₂ and Ar. The resulting spectra are very intense and the 0-0, 1-1, 1-0 bands of A ² Π _1/2-X ² Σ ⁺ sub-transition and the 0-0 band of A ² Π _3/2-X ² Σ ⁺ sub-transition have been rotationally analyzed. Improved molecular constants have been derived using a least-squares fit program in which optical data of earlier analyzed 0-1 and 0-2 bands (A ² Π _1/2-X ² Σ ⁺) was also included. The Λ-doubling constants in the v′ = 0, 1 levels of the A ² Π _1/2 sub-state are as expected, i.e. p ₁ > p ₀, where as it is found that the spin-doubling constants of the v″ = 0, 1 and 2 levels of the ground state X ² Σ ⁺, decrease with the increase in v, i.e. γ ₀ > γ ₁ > γ ₂. This is indicative of the presence of some nearby state, influencing the spin-doubling.     

Rotational distribution of nascent OH radicals after H2O2 photolysis at 193 nm

The rotational distribution of OH(X ²,v=0) radicals was investigated by resonant laser-induced fluorescence (LIF) after photolysis of H₂O₂ at 193 nm. A microcomputer equipped LIF arrangement allowed special shot-by-shot normalization of the fluorescence signal for noise reduction. Using a least-squares procedure we were able to account for all measured line intensities including overlapping lines (blends) and obtain a complete rotational state distribution of the OH(X ²,v=0) state. The rotational excitation shows a Gaussian-like distribution with a maximum atK=12 and with 16% of the total available energy (17,400 cm^–1) appearing in rotation. Only 1% of the available energy is converted into vibration, leaving over 83% for translational excitation. The measured rotational distribution appears to fit a semiclassical theory.     

Parametric four-wave mixing in the H2Σ+,H′2Π(v′=0) states of NO

2 Σ⁺,H^′2Π(v^′=0)←X²Π(v^′′=0) two-photon transition of NO, both near-infrared and vacuum ultraviolet radiation were emitted along the laser propagation direction. The analyses of emission and excitation spectra revealed that the parametric four-wave mixing (PFWM) process coexisted with amplified spontaneous emission. Polarization properties of the IR radiation are found to be dependent on the rotational levels. Pressure and laser power behaviors of the generated waves were reported. The mechanism of PFWM was discussed in terms of selection rules of the relevant ro-vibronic transitions. Received: 19 September 1996/Revised version: 27 January 1997     

Intensity distribution in theA 2Π –X 2Σ+ system of Yttrium monoxide

The integrated intensities of a few bands in the vibrational structure of the astrophysically significant ‘orange’ system of the molecule yttrium monoxide, have been measured experimentally by the technique of photographic photometry. The effective vibrational temperatures of the source are found to be 2402±180 K and 2901±230 K for the subsystemsA ²Π_3/2−X ² Σ ⁺ andA ²Π_1/2−X ² Σ ⁺ respectively.     

Calculation of adiabatic potentials of Li<Subscript>2</Subscript><Superscript>+</Superscript>

We report adiabatic potential energy curves of the Li₂ ⁺ molecule. Our curves are tabulated according to internuclear distance from 2 a₀ to 100 a₀. We compare our theoretical results with the ones calculated by other authors and potential energy curves derived from experiments. For the ground state and 17 excited states we calculate spectroscopic parameters and compare them with parameters obtained by other authors. For the first time we present three new minima for 3²Σ_u ⁺, 4²Σ_u ⁺ and 2²Π_g excited states. In our approach we use the configuration interaction method where only the valence electrons of Li atoms are treated explicitly. The core electrons are represented by pseudopotential. All calculations are performed by means of MOLPRO program package.